Milky Way galaxy's Great Rift
Space is the void and the physical universe that exists outside Earth's atmosphere and between celestial bodies. Space is a near-perfect vacuum with little matter, save for dispersed particles, radiation, dark matter and dark energy.
Space is virtually limitless, and its size is difficult to define or comprehend. Scientists estimate there are more than 100 billion galaxies in space, with the largest containing 400 billion stars. Our galaxy, the Milky Way, has 100 billion stars. Other celestial bodies, such as planets, nebulae, asteroids, black holes, quasars, etc. litter space as well. Owing to space's incalculable size, these objects are often immense, numerous in number and spread vastly far apart from each other.
Humans developed adequate technology and began exploring space in the 20th century. While space agencies such as NASA have launched various probes and unmanned spacecraft to explore our solar system, humans themselves have only landed on the moon thus far. Advancements in telescope technology, however, have given us a remarkably sweeping view across the known universe. (Photo: Shutterstock)

8 pioneering black women in science, technology and medicine

England launches 'cosmic census' to combat light pollution

Satellite snaps first-ever group shot of Earth and the moon's far side

Dark side of the universe could be way more complicated than the light side

This new 3D map of our galaxy features 1.7 billion stars

The first image of a black hole is almost ready

Scientists create a 'Star Trek'-style replicator

What to see in the night sky in February

NASA to test new weapon against asteroids

This rock brought back from the moon likely came from Earth

Planetary collision seeded elements for life on Earth, study says

A meteorite smashed into the blood moon during the eclipse, and it was caught on film